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Tom Sanford

Senior Principal Oceanographer Emeritus

Professor Emeritus, Oceanography





Research Interests

Physical Oceanography; Instrumentation; Structure and Dynamics of Currents, Eddies and Waves; Propagation and Dissipation of Internal Waves


Dr. Sanford conducts innovative, high-quality basic and applied oceanographic research, teaches graduate students, mentors postdoctoral researchers, and fosters collaborations with national and international investigators and organizations. Broadly, his research exploits motional induction theory — the motion of seawater through the Earth's magnetic field that produces electric currents and magnetic fields — to infer important aspects of ocean properties and kinetic structure. These methods have been applied to a range of studies in the open ocean and within channels. In nearly five decades as an experimental physical oceanographer, Sanford has participated in many dozen cruises and research projects, provided the oceanographic community with important results, and developed several instruments and new observational methods. Recent efforts include the development of two ocean velocity sensors, one an autonomous vertical profiler (EM-APEX) and the other a bottom lander (HPIES). Prior to these, he led the development of the XCP, an expendable current profile. These are being used to study upper-ocean mixing and convective processes, interactions between internal waves and steady currents, momentum flux into the ocean (such as from hurricanes), as well as the structure and variability of oceanic boundary and estuarine currents.

As Professor in the UW School of Oceanography, Dr. Sanford has taught courses and advised advanced research for about two-dozen graduate students and postdocs. Dr. Sanford is a Fellow of the American Geophysical Union and American Meteorological Society, received the IEEE/Ocean Engineering Society 2008 Distinguished Technical Achievement Award and in 2010 the AMS Henry Stommel Research Award. Since 2008 he has served as an ONR Secretary of the Navy/Chief of Naval Operations Chair of Oceanographic Sciences.

Department Affiliation

Ocean Physics


A.B. Physics, Oberlin College, 1962

Ph.D. Physical Oceanography, Massachusetts Institute of Technology, 1967


Origins of the Kuroshio and Mindanao Currents

The boundary currents off the east coast of the Philippines are of critical importance to the general circulation of the Pacific Ocean. The westward flowing North Equatorial Current (NEC) runs into the Philippine coast and bifurcates into the northward Kuroshio and the southward Mindanao Current. Quantifying these flows and understanding bifurcation dynamics are essential to improving predictions of regional circulation and Pacific Ocean climate. We have deployed five HPIES off NE Luzon Island under the Kuroshio and nine EM-APEX floats in the NEC as it flows westward toward the Philippine Islands.

8 May 2013

Lateral Mixing

Small scale eddies and internal waves in the ocean mix water masses laterally, as well as vertically. This multi-investigator project aims to study the physics of this mixing by combining dye dispersion studies with detailed measurements of the velocity, temperature and salinity field during field experiments in 2011 and 2012.

1 Sep 2012


2000-present and while at APL-UW

Estimates of surface waves using subsurface EM-APEX floats under Typhoon Fanapi 2010

Hsu, J.-Y., R.-C. Lien, E.A. D'Asaro, T.B. Sanford, "Estimates of surface waves using subsurface EM-APEX floats under Typhoon Fanapi 2010," J. Atmos. Ocean. Technol., 35, 1053-1075, doi:10.1175/JTECH-D-17-0121.1, 2018.

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1 May 2018

Seven subsurface Electromagnetic Autonomous Profiling Explorer (EM-APEX) floats measured the voltage induced by the motional induction of seawater under Typhoon Fanapi in 2010. Measurements were processed to estimate high-frequency oceanic velocity variance associated with surface waves. Surface wave peak frequency fp and significant wave height Hs are estimated by a nonlinear least squares fitting to oceanic velocity, assuming a broadband JONSWAP surface wave spectrum. The Hs is further corrected for the effects of float rotation, Earth's geomagnetic field inclination, and surface wave propagation direction. The fp is 0.08–0.10 Hz, with the maximum fp of 0.10 Hz in the rear-left quadrant of Fanapi, which is ~0.02 Hz higher than in the rear-right quadrant. The Hs is 6–12 m, with the maximum in the rear sector of Fanapi. Comparing the estimated fp and Hs with those assuming a single dominant surface wave yields differences of more than 0.02 Hz and 4 m, respectively. The surface waves under Fanapi simulated in the WAVEWATCH III (ww3) model are used to assess and compare to float estimates. Differences in the surface wave spectra of JONSWAP and ww3 yield uncertainties of <5% outside Fanapi’s eyewall and >10% within the eyewall. The estimated fp is 10% less than the simulated ww3 peak wave frequencey before the passage of Fanapi’s eye and 20% less after eye passage. Most differences between Hs and simulated ww3 significant wave height are <2 m except those in the rear-left quadrant of Fanapi, which are ~5 m. Surface wave estimates are important for guiding future model studies of tropical cyclone wave–ocean interactions.

Downstream evolution of the Kuroshio's time-varying transport and velocity structure

Andres, M., V. Mensah, S. Jan, M.-H. Chang, Y.-J. Yang, C.M. Lee, B. Ma, and T.B. Sanford, "Downstream evolution of the Kuroshio's time-varying transport and velocity structure," J. Geophys. Res., 122, 3519-3542, doi:10.1002/2016JC012519, 2017.

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1 May 2017

Observations from two companion field programs—Origins of the Kuroshio and Mindanao Current (OKMC) and Observations of Kuroshio Transport Variability (OKTV)—are used here to examine the Kuroshio's temporal and spatial evolution. Kuroshio strength and velocity structure were measured between June 2012 and November 2014 with pressure-sensor equipped inverted echo sounders (PIESs) and upward-looking acoustic Doppler current profilers (ADCPs) deployed across the current northeast of Luzon, Philippines, and east of Taiwan with an 8 month overlap in the two arrays' deployment periods. The time-mean net (i.e., integrated from the surface to the bottom) absolute transport increases downstream from 7.3 Sv (±4.4 Sv standard error) northeast of Luzon to 13.7 Sv (±3.6 Sv) east of Taiwan. The observed downstream increase is consistent with the return flow predicted by the simple Sverdrup relation and the mean wind stress curl field over the North Pacific (despite the complicated bathymetry and gaps along the North Pacific western boundary). Northeast of Luzon, the Kuroshio—bounded by the 0 m s–1 isotach—is shallower than 750 dbar, while east of Taiwan areas of positive flow reach to the seafloor (3000 m). Both arrays indicate a deep counterflow beneath the poleward-flowing Kuroshio (–10.3 ± 2.3 Sv by Luzon and –12.5 ± 1.2 Sv east of Taiwan). Time-varying transports and velocities indicate the strong influence at both sections of westward propagating eddies from the ocean interior. Topography associated with the ridges east of Taiwan also influences the mean and time-varying velocity structure there.

Estimates of surface wind stress and drag coefficients in Typhoon Megi

Hsu, J.-Y., R.-C. Lien, E.A. D'Asaro, and T.B. Sanford, "Estimates of surface wind stress and drag coefficients in Typhoon Megi," J. Phys. Oceanogr., 47, 545-565, doi:10.1175/JPO-D-16-0069.1, 2017.

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1 Mar 2017

Estimates of drag coefficients beneath Typhoon Megi (2010) are calculated from roughly hourly velocity profiles of three EM-APEX floats, air launched ahead of the storm, and from air-deployed dropsondes measurements and microwave estimates of the 10-m wind field. The profiles are corrected to minimize contributions from tides and low-frequency motions and thus isolate the current induced by Typhoon Megi. Surface wind stress is computed from the linear momentum budget in the upper 150 m. Three-dimensional numerical simulations of the oceanic response to Typhoon Megi indicate that with small corrections, the linear momentum budget is accurate to 15% before the passage of the eye but cannot be applied reliably thereafter. Monte Carlo error estimates indicate that stress estimates can be made for wind speeds greater than 25 m s-1; the error decreases with greater wind speeds. Downwind and crosswind drag coefficients are computed from the computed stress and the mapped wind data. Downwind drag coefficients increase to 3.5 ± 0.7 x 10-3 at 31 m s-1, a value greater than most previous estimates, but decrease to 2.0 ± 0.4 x 10-3 for wind speeds > 45 m s-1, in agreement with previous estimates. The crosswind drag coefficient of 1.6 ± 0.5 x 10-3 at wind speeds 30–45 m s-1 implies that the wind stress is about 20° clockwise from the 10-m wind vector and thus not directly downwind, as is often assumed.

More Publications


Remote Sensing of Salinity Profiles in a Marine Estuary

Record of Invention Number: 47312

Tom Sanford, Jim Carlson, John Dunlap


22 Apr 2015

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center